ESXi: What it is and why it’s useful

The native hypervisor ESXi doesn’t need its own a general-purpose operating system and is thus very efficient with space and resources. ESXi is mostly used for virtualising servers.

VMware’s ESXi is a type 1 hypervisor, also known as a bare metal hypervisor, that’s installed directly on a physical server and can be used independently of any operating system. The software vSphere is used for administration. ESXi is based on the VMkernel and doesn’t need its own underlying operating system, meaning that it uses significantly less space than other hypervisors. VMware launched ESXi in 2001 and still offers it today. ESXi stands for ‘Elastic Sky X integrated’.

Hypervisors are the layer between a purely virtual machine and the physical system it runs on. The software makes it possible to manage the virtual and the physical components involved, allocates tasks and storage space, and ensures that different machines can run on the same system without getting in each other’s way. Hypervisors are divided into two types: type 1 hypervisors, which aren’t connected to the host’s operating system, and type 2 hypervisors, which require an existing operating system. ESXi is a type 1 hypervisor.

ESX was the predecessor to VMware’s ESXi and was also a type 1 hypervisor. Unlike ESXi, ESX had its own service console. That means that it used significantly more storage space than ESXi. ESX has been out of use since version 5.0 of vSphere, due to the significant advantages of ESXi in terms of installation and storage space.

ESXi is especially popular when it comes to the virtualisation of servers and boasts excellent results in this regard. With simple horizontal and vertical scalability, ESXi not only provides optimal options for partitioning but also enables you to work securely on one or more machines. It’s also used for (temporarily) separate servers and virtual test environments.

ESXi comes with a number of advantages, especially compared with its predecessor ESX, which used significantly more memory. Virtualising entire data centres can save money, resources, and space without compromising on reliability and security. Thanks to its proximity to hardware, ESXi boasts strong performance and makes optimal use of available resources. Management is centralised in the hypervisor and the virtualised systems can be easily exported. A high level of flexibility and quick installation are additional advantages. If your ESXi server is rented, you’ll save even more money. And as mentioned above, you’ll have numerous options for scaling.

The software vSphere is used for managing ESXi and is available in both free and paid versions. With the completely free version VMware vSphere Hypervisor, you won’t be able to communicate with vCenter servers and can only manage each host individually. The paid versions all differ in price and their range of features. The maximum number of servers will also vary based on which pricing package you choose.

There are a number of free and paid alternatives to ESXi. One of the most popular open source solutions is Citrix XenServer, which is not only free but also relatively easy to use. However, compared with commercial offerings, the range of features is rather limited. The same is true of Proxmox VE and KVM. Hyper-V by Microsoft is available for Windows servers and client operating systems. Like ESXi/vSphere, this hypervisor is available in different price models.